1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly, it is concerned with a magnetic tape whose coefficient of friction is decreased and travelling durability is improved without lowering the S/N and whose edge band or nick is prevented.
2. Description of the Prior Art
In magnetic recording tapes for audio, video and computers, in general, the surface of the magnetic recording layer is finished smooth so as to improve the sensitivity, in particular, the output in high frequency range. However, such a smooth magnetic recording tape has a tendency that it is not taken up regularly during taking-up or rewinding, thus resulting in a disordered wound state. The use of this magnetic recording tape often results in, due to fluctuation of its tension, deterioration of the tape running property, fluctuation of the output and deformation or breakage of the tape.
In order to ovrcome the above described disadvantage, there has hitherto been proposed a magnetic recording tape provided with a back layer on the surface of a support opposite to the magnetic recording layer, and vinyl chloride-vinyl acetate copolymers have been used as a binder for the back layer. In this case, however, there are still drawbacks that the abrasion resistance or toughness is low, the running durability is unfavourably affected, the coefficient of friction is increased and the tape tends to be doubled, and thus there is room for improvement.
Furthermore, it is well known that when a magnetic recording medium, in particular, magnetic recording tape, provided with a back layer to improve the tape running property or running durability is rolled up or piled up in sheets, the roughness of the back layer is transferred to the surface of the magnetic layer, thus resulting in deterioration of the surface property of the magnetic layer and lowering of the electromagnetic properties, in particular, S/N property of the magnetic recording medium. As a result of thinking much of the running property of the back layer, its surface state is rough so that when the magnetic recording medium is stored or allowed to stand under rolled or piled state, the roughness of the back layer is transferred to the surface of the magnetic layer.